Recent news
Publications
Aaron L. Holsteen; Ahmet Fatih Cihan; Mark L. Brongersma
Temporal color mixing and dynamic beam shaping with silicon metasurfaces Journal Article
In: Science, vol. 365, no. 6450, pp. 257-260, 2019.
@article{holsteen2019temporal,
title = {Temporal color mixing and dynamic beam shaping with silicon metasurfaces},
author = {Aaron L. Holsteen and Ahmet Fatih Cihan and Mark L. Brongersma},
doi = {10.1126/science.aax5961},
year = {2019},
date = {2019-07-19},
journal = {Science},
volume = {365},
number = {6450},
pages = {257-260},
abstract = {Metasurfaces offer the possibility to shape optical wavefronts with an ultracompact, planar form factor. However, most metasurfaces are static, and their optical functions are fixed after the fabrication process. Many modern optical systems require dynamic manipulation of light, and this is now driving the development of electrically reconfigurable metasurfaces. We can realize metasurfaces with fast (\>105 hertz), electrically tunable pixels that offer complete (0- to 2π) phase control and large amplitude modulation of scattered waves through the microelectromechanical movement of silicon antenna arrays created in standard silicon-on-insulator technology. Our approach can be used to realize a platform technology that enables low-voltage operation of pixels for temporal color mixing and continuous, dynamic beam steering and light focusing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Metasurfaces offer the possibility to shape optical wavefronts with an ultracompact, planar form factor. However, most metasurfaces are static, and their optical functions are fixed after the fabrication process. Many modern optical systems require dynamic manipulation of light, and this is now driving the development of electrically reconfigurable metasurfaces. We can realize metasurfaces with fast (>105 hertz), electrically tunable pixels that offer complete (0- to 2π) phase control and large amplitude modulation of scattered waves through the microelectromechanical movement of silicon antenna arrays created in standard silicon-on-insulator technology. Our approach can be used to realize a platform technology that enables low-voltage operation of pixels for temporal color mixing and continuous, dynamic beam steering and light focusing.
Ahmet Fatih Cihan
Control of directionality of light with active and passive silicon nanostructures PhD Thesis
Stanford University, 2018.
@phdthesis{AhmetFatihCihanthesis,
title = {Control of directionality of light with active and passive silicon nanostructures},
author = {Ahmet Fatih Cihan},
url = {http://purl.stanford.edu/hv870mn3942},
year = {2018},
date = {2018-12-01},
school = {Stanford University},
abstract = {Semiconductor nanoantennas have recently emerged as very promising platforms for light manipulation at the nanoscale. More specifically, Silicon has become very popular among researchers thanks to its strong light-matter interaction features, mature fabrication technology availabilities, potential for serving simultaneous optical and electronic purposes, and significantly lower losses compared to its metallic competitors. In this thesis, we employed two main architectures that help us achieve our ultimate goal of controlling the light emission and scattering properties in the nanoscale. In the first architecture, we utilize Si nanowires as our nanoantennas to control the emission directionality of 2D monolayer MoS2 emitters, where our choice of emitter material was based on the attractive properties and recent popularity of 2D materials emitting in the visible range of the spectrum. In this Si- MoS2 configuration, we demonstrate more than 25 top-to-bottom emission ratio enhancement with Si NWs compared to bare MoS2 emission. By using NWs of different radii, we demonstrated such directionality by two different mechanisms which were fundamentally different in terms of the excited resonances in the NW. While targeting directionality, we also observed strong polarization selectivity and spectral modification of the operation principles which gave us the power to tune the spectral and polarization properties of the dominant top emission of this system. As the next step, we aimed to demonstrate an active and on-demand control of directionality of scattering of plane-waves. To achieve this, we designed, fabricated and characterized a Si MEMS architecture that enabled us to observe more than 30° active control of angular emission with the application of 5 V potential.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Semiconductor nanoantennas have recently emerged as very promising platforms for light manipulation at the nanoscale. More specifically, Silicon has become very popular among researchers thanks to its strong light-matter interaction features, mature fabrication technology availabilities, potential for serving simultaneous optical and electronic purposes, and significantly lower losses compared to its metallic competitors. In this thesis, we employed two main architectures that help us achieve our ultimate goal of controlling the light emission and scattering properties in the nanoscale. In the first architecture, we utilize Si nanowires as our nanoantennas to control the emission directionality of 2D monolayer MoS2 emitters, where our choice of emitter material was based on the attractive properties and recent popularity of 2D materials emitting in the visible range of the spectrum. In this Si- MoS2 configuration, we demonstrate more than 25 top-to-bottom emission ratio enhancement with Si NWs compared to bare MoS2 emission. By using NWs of different radii, we demonstrated such directionality by two different mechanisms which were fundamentally different in terms of the excited resonances in the NW. While targeting directionality, we also observed strong polarization selectivity and spectral modification of the operation principles which gave us the power to tune the spectral and polarization properties of the dominant top emission of this system. As the next step, we aimed to demonstrate an active and on-demand control of directionality of scattering of plane-waves. To achieve this, we designed, fabricated and characterized a Si MEMS architecture that enabled us to observe more than 30° active control of angular emission with the application of 5 V potential.
Ahmet Fatih Cihan; Alberto G. Curto; Søren Raza; Pieter G. Kik; Mark L. Brongersma
Silicon Mie resonators for highly directional light emission from monolayer MoS2 Journal Article
In: Nature Photonics, vol. 12, pp. 284-290, 2018.
@article{CihanMoS2,
title = {Silicon Mie resonators for highly directional light emission from monolayer MoS2},
author = {Ahmet Fatih Cihan and Alberto G. Curto and S\oren Raza and Pieter G. Kik and Mark L. Brongersma},
doi = {10.1038/s41566-018-0155-y},
year = {2018},
date = {2018-04-23},
journal = {Nature Photonics},
volume = {12},
pages = {284-290},
abstract = {Controlling light emission from quantum emitters has important applications, ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries such as wires and spheres support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a silicon nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a silicon nanowire.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Controlling light emission from quantum emitters has important applications, ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries such as wires and spheres support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a silicon nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a silicon nanowire.
